Changes in the motor response threshold to direct electric stimulation of the motor cortex during elaboration of conditioned reflex switching-over

During elaboration of switching-over of an alimentary salivary conditioned reflex to a defensive one in dogs, with foreleg passive flexion as a signal stimulus, excitability changes of opposite signs appeared in the cortical representation of the left foreleg. At the stage of elaborated switching-over, the threshold of the flexor reaction to a direct stimulation of the motor cortex became lower in the alimentary experimental situation (passive rise--milk) and rose in the defensive situation (passive rise--acid).